Evaluate the magnitude of the gravitational field at the surface of the planet

The trajectory of a rock thrown from a height with an initial speed of 16.9 m/s is shown in the figure below. Evaluate the magnitude of the gravitational field at the surface of the planet. The planet has no atmosphere.

You don't know the mass of the planet, or its radius, so you can't use the first equation; and the second equation is for centripetal acceleration

All you're being asked is to measure the acceleration on the graph (you can assume it's vertical, and a constant).

"All you're being asked is to measure the acceleration on the graph (you can assume it's vertical, and a constant)" => you mean a = 10 m/s^2 (when I look at the vertical on the graph) ??? I'm confused...

Suppose you throw away a rock from an alitude of 10m with a speed v=16.9m and with an angle of [itex] \phi [/itex] with the horizontal on a planet with acceleration of gravity a.
you should be able to calculate the maximum altitude and the range as a function of a and [itex] \phi [/itex]

Now you can read the maximum altitude and the range from the graph, so you get to equations
for a and [itex] \phi [/itex] that you can solve.

Suppose you throw away a rock from an alitude of 10m with a speed v=16.9m and with an angle of [itex] \phi [/itex] with the horizontal on a planet with acceleration of gravity a.
you should be able to calculate the maximum altitude and the range as a function of a and [itex] \phi [/itex]

Now you can read the maximum altitude and the range from the graph, so you get to equations
for a and [itex] \phi [/itex] that you can solve.

Got ya. Do you have any ideas about equation calculator here? That's would be great ;)